U.S. Pat. No. 6,540,441 describes a transporter for removing offshore jacket structures, said transporter having an elongate cradle-like structure made from tubular elements. The cradle-like structure has a U-shaped cross section. When approaching a jacket structure to be removed, the transporter is rotated 90° and floated in vertical orientation so as to embrace the jacket on three sides. After the transporter has been attached to the jacket and the legs of the jacked severed, the transporter with the jacket is raised through de-ballasting and rotated back to the horizontal position before being towed to a predetermined destination for the jacket. Even though the transporter in its vertical position is moved towards the jacket both by means of tugs and winches, it has a quite substantial water line area which makes it prone to uncontrolled movements caused by environmental forces like waves, such movements being particularly critical in the connecting phase since the jacked could easily be damaged. The transporter according to U.S. Pat. No. 6,540,441 also has the drawback of being larger than necessary in the sense that it has about twice as much buoyancy as necessary for carrying the jacket structure. This is because the sides of the U-shaped cradle will be entirely above the water in a towing situation.
The purpose of the present invention is to alleviate the drawbacks mentioned above and to provide a method and vessel that will permit the vessel to approach the jacket structure in a safe and controlled manner also under inclement weather conditions, while the shape of the vessel is such that it has little excess buoyancy and is easy to build with common shipyard technology and equipment.
This is obtained according to the invention by a method as recited in claim 1 and a vessel as recited in claim 5. Advantageous embodiments of the inventions are recited in the respective dependent claims.
For better understanding of the invention it is referred to the following description of the exemplifying embodiment shown in the appended drawings.